Device-to-device (“D2D”) communications have been considered one of the key techniques in the 3rd Generation Partnership Project (3GPP) Long Term Evolution Advanced (LTE-A) standards, where it provides direct communication among pieces of user equipment (“UEs”) in close proximity. As per the 3GPP standard TS 23.303 Release 12, D2D communication among UEs is enabled by a Proximity Service (“ProSe”) function server.
The inventors here have recognized several technical problems with such conventional systems, as explained below. In 3GPP standard TS 23.303 Release 12, there is no admission control mechanism for D2D communications among UEs. Since there is no admission control mechanism, the existing ProSe function server as provided in 3GPP standard TS 23.303 Release 12 gets overloaded when the number of devices and number of simultaneous D2D communication links increases in a network. This results in packet drop and decreases Quality of Service (“QoS”).
In a scenario where several D2D discovery request messages from multiple UEs arrive at the ProSe function server, the signaling load at the ProSe function server increases. Also, if the ProSe function server fails to respond to received discovery request messages, then the D2D-enabled UEs cannot perform their communication, hence causing a loss of QoS.
Currently, the ProSe function server honors discovery requests solely based on subscription information (entitlement) of each UE, which leads to the following limitations. First, the ProSe function server is not designed to handle multiple discovery requests at any instant. This means that the ProSe function server will honor a single discovery request at any instant, and refuse/drop the rest, thus not allowing many initiator UEs to start D2D communication.
Second, the ProSe function server fails to differentiate among discovery requests from UEs with different levels of criticality. This may result in allowance of D2D communication to an incorrect/improper initiator UE and dropping of a more critical initiator UE out of the set of initiator UEs that had sent discovery requests simultaneously at any instant.
However, for maintaining the QoS of initiator UEs in a network, it is desired for the ProSe function server to have the following capabilities. First, it it desired that the ProSe function server be capable of handling multiple discovery requests at any instant. Second, it is desired that the ProSe function server be capable of differentiating among discovery requests coming from initiator UEs with different levels of criticality, and ensuring that the most appropriate ones are allowed in order to maintain QoS.